What is metabolism in cellular biology?
The set of chemical reactions producing or using energy and transforming matter in cells.
What role does an enzyme play in a chemical reaction?
It catalyzes the reaction without being consumed as a reactant.
What does anabolism consist of?
Synthesis pathways that build molecules.
What does catabolism consist of?
Degradation pathways that break molecules down.
What is a molecule?
A group of atoms joined by chemical bonds.
What is an atom in terms of chemical combination?
The smallest part of a simple body that can chemically combine with another atom.
What is the smallest structural and functional unit of living organisms?
A cell.
What does the plasma membrane do for the cell?
It delimits the cell and permits regulated exchanges with its environment.
What main components does a eukaryotic cell contain?
A nucleus, cytoplasm, and membrane-bound organelles such as mitochondria.
What does cellular compartmentalization assign to specialized locations?
Specialized tasks.
Give an example of specialized tasks assigned by cellular compartmentalization.
Mechanical work to muscle cells and electrical work to nerve cells.
What does metabolic regulation maintain despite environmental changes?
Relatively constant living conditions.
What triggers metabolic regulation to maintain constant conditions?
Internal and external signals.
What is anabolism in metabolism?
The synthesis of small molecules and macromolecules from simple nutrients or intermediates.
What does anabolism require to proceed?
An energy supply.
What is catabolism in metabolism?
The production of energy through oxidation and degradation of nutrients and reserves.
What types of energy does catabolism produce?
Chemical, electrical, or mechanical energy.
How is part of the chemical energy from catabolism stored?
As ATP.
What distinguishes aerobic metabolism from anaerobic metabolism?
Aerobic metabolism uses oxygen, anaerobic does not.
What are the products of aerobic glucose oxidation?
Water, carbon dioxide, heat, and ATP are produced.
How long does the alactic anaerobic system support intense effort?
Approximately 20 seconds.
What duration and effect characterize the lactic anaerobic system?
It supports about 2 minutes of effort and may cause cramps from lactate.
What causes ischemia during myocardial infarction?
Arterial occlusion reduces oxygen delivery causing ischemia.
What is ATP's role in energy use?
ATP acts as an immediate energy intermediary or is hydrolyzed when energy is needed.
Where does most ATP production occur in the cell?
70–80% of ATP production occurs in mitochondria.
What percentage of ATP production occurs in the cytosol?
Approximately 20–30% of ATP production occurs in the cytosol.
How does mitochondrial oxidative phosphorylation synthesize ATP?
It uses a proton flow generated by oxidation pathways to synthesize ATP.
What role does oxygen play in mitochondrial ATP synthesis?
Oxygen contributes to water formation during ATP synthesis.
What percentage of total energy expenditure is resting energy expenditure?
Resting energy expenditure represents 60–70% of total energy expenditure.
What functions does resting energy expenditure support?
It supports vital functions, resting muscle tone, and active ion transport.
How much of total energy expenditure does physical activity represent in sedentary people?
Physical activity represents 20–25% of total energy expenditure in sedentary people.
What role do metabolic intermediates play in metabolism?
They connect carbohydrate, lipid, and protein pathways with energy storage.
Where is glycogen mainly stored in the body?
In muscle and liver tissues.
Where are lipids primarily stored in the body?
In adipose tissue.
What processes does ATP support related to metabolism?
Glycogen synthesis, lipid synthesis, protein detoxification, and sodium pumping.
How does insulin function after food intake?
It promotes storage or synthesis of carbohydrates, lipids, and proteins.
What are the first priorities during fasting?
Maintaining blood glucose for brain and red blood cells and preserving muscle protein mass.
Which process releases glucose from glycogen stores in the first fasting phase?
Glycogenolysis.
How long does the first fasting phase using glycogenolysis last?
Approximately 48 hours.
What process synthesizes glucose from amino acids in the second fasting phase?
Gluconeogenesis.
What is a risk of gluconeogenesis during the second fasting phase?
Threatens muscle protein mass.
Why don't lipids produce glucose during the lipid phase of fasting?
Because the metabolic pathway to convert lipids into glucose does not exist.
What happens in the final stage of fasting that compromises vital prognosis?
Depletion of 54% of the vital metabolic compartment.
How long can survival last with water and mineral salts during fasting?
45–65 days depending on individual reserves.
Test your knowledge with 24 questions on Metabolism and Energy Balance.
1. What does metabolism encompass in a living organism?
2. What role does an enzyme play in a cellular chemical reaction?
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